1. Field of the Invention
The present invention relates to improvements in or relating to underwater vehicles.
2. Description of the Related Art
It is known to use a wire command link to connect an underwater vehicle to its launch platform to provide an exchange of information between the underwater vehicle and the launch platform. The wire command link comprises a copper guidewire which is payed-out from the underwater vehicle as it moves through the water.
The command link comprises two interconnected spools of guidewire, one of which is mounted on the underwater vehicle and the other of which is mounted on the launch platform. The spool of guidewire on the launch platform may pay-out through a weighted metal hosepipe which falls, due to gravity, to a position below the launch platform to prevent entanglement of the guidewire with the structure and/or propulsion system of the launch platform. The spool of guidewire on the underwater vehicle unwinds and pays-out from the rear of the underwater vehicle.
Prior to launch of the underwater vehicle using a command link within a hosepipe, the hosepipe is neatly coiled within a launch tube in the launch platform and is connected by a weak link to the rear of the underwater vehicle which is also located within the launch tube. During the launch phase, the underwater vehicle pulls the hosepipe out of the launch tube until fully deployed, when the weak link separates and the hosepipe falls to a position below the launch platform. The guidewire then pays-out from both spools as the underwater vehicle and the launch platform operate and/or manoeuvre independently.
In other underwater vehicle configurations where a command link within a hosepipe is not used the guidewire may pay out directly the launch sequence of the underwater vehicle is commenced.
Whilst copper guidewire is very robust and can be easily jointed and insulated using conventional techniques, there is a move to replace copper guidewire with optical fibres or microcables. Such optical fibres and microcables are, however, quite fragile, and have bend radius limitations. Such optical fibres and cables require a specialised jointing process such as fusion splice techniques.
In fusion splice techniques, lengths of optical fibres or microcables between 0.5 and 1 m are required on each optical fibre or microcable to be available so that the fusion splice technique can be carried out effectively and efficiently. This means that, after the joint has been made, up to 2 m of optical fibre or microcable remains outside the coils of fibre or cable stored in the spools of guidewire in the underwater vehicle and the launch platform where it is vulnerable to damage due to its fragility.
International patent application number PCT/GB02/05789 discloses a means for providing storage, in the form of a splice chamber, between the launch platform and the underwater vehicle for the fusion splice joint and any excess fibre or cable of a command wire having a hosepipe. The splice cavity also provides protection for the fusion splice joint during the launch phase. The splice chamber is mounted between the outboard end of the hosepipe connected to the launch platform and to an underwater vehicle. During the launch sequence the splice chamber containing the splice and the excess optical fibre or microcable is released from the underwater vehicle and splits in two, falling clear of the underwater vehicle, allowing the optical fibre or microcable guidewire to pay out from both the spool in the launch platform and the spool in the underwater vehicle.
However, it is not always desirable to release an object from the underwater vehicle, during the launch sequence due to the potential for fouling on the underwater vehicle, the launch platform or any other object.